The project is to investigate the maturation of 5-hydroxytryptamine, (5-HT) metabolism in the mouse brain. Using drugs and metabolic pathway precursors, intermediates and end products the mechanisms which control and regulate the brain's indoleamine maturation will be sought. The problem is to be approached from a biochemical, physiological and behavioral basis. In vitro biochemical assay methods, thermoregulatory capability and simple behavioral tests will be employed to reflect the maturational process following specific experimental manipulations. Similar studies of maturing mouse lateral eyes and larval toad brains are also to be considered. Involvement of truptophan loading and peripheral decarboxylase upon the maturational process in the mouse is to be specifically tested. Multiple enzyme forms and their change with time are to be considered as well.